1) Oooh, a Huge Animal Sound Archive Goes Online". "An archive of tens of thousands of animal sounds has just gone online." The Machaulay Library sound collection is free, searchable, and just plain fun; the comments with the recoding are also interesting. There are also plans for a guide to North American Bird sounds sometime this spring, so it's definitely worth watching. I drove my lovebird nuts listening to blackbird calls.
The library also has a side link for Sound Analysis software (quite free), but I haven't gotten to try it out yet because the internet had a bad case of the slows. All I can say is, it looks like a neat idea.
2) And here, on Wired's GeekDad, is Music and Science Combine for the Win With Songs for Unusual Creatures" by Michael Hears and the Kronos Quartet. There's an embedded video there of the second song, featuring the Aye-Aye.
3) Or you can "Listen: the Music of a Human Brain", work done by Jing Lu and Dezhong Yao of China’s University of Electronic Science and Technology. Their work "translates a brain’s electrical fluctuations to pitch and blood flows to intensity." I just wish the samples weren't so short.